Synthesis of lanthanum-alkaline earth-copper-oxygen superconductive material

Abstract

A mixture comprised of an alkali chloride solvent and reactants comprised of oxides of lanthanum, an alkaline earth and copper, wherein the reactants are formulated to produce a superconducting reaction product, is heated to melt the chloride solvent in which the reactants then dissolve and react precipitating a lanthanum-alkaline earth-copper-oxygen superconductive material.

what is claimed is: 
     
       1. A process of making a superconductive composition in polycrystalline powder form having the formula La 2-x  A x  CuO 4-y , wherein A is strontium or barium, x is from about 0.1 to 0.2 and y is from 0 to about 0.2, which comprises forming an admixture comprising an alkali metal chloride solvent material selected from the group consisting of sodium chloride and potassium chloride, the oxide or oxide precursors of lanthanum and copper and an oxide or oxide precursor of at least one member of the group consisting of barium and strontium in amounts sufficient to produce the superconductive composition by reaction; heating the admixture to a temperature sufficient to melt the alkali metal chloride and at least partially dissolve the oxides of lanthanum, barium, strontium, and copper and form said superconductor composition; maintaining said temperature until the oxides are substantially consumed by formation of the superconductive composition; cooling the molten solvent material to a solid; separating and recovering the superconductive composition in powder by dissolving the alkali metal solvent material in water. 
     
     
       2. A process according to claim 1 for making, by precipitation from a molten chloride solvent, a superconductive composition in polycrystalline powder form having the formula La 2-x  A x  CuO 4-y , wherein A is strontium or barium, x is from about 0.1 to 0.2 and y is from 0 to about 0.2, which comprises forming an admixture comprising an alkali metal chloride selected from the group consisting of sodium chloride and potassium chloride, lanthanum oxide, cupric oxide and member of the group consisting of barium carbonate and strontium carbonate, in amounts sufficient to produce the superconductive composition by reaction; heating the admixture to a temperature sufficient to melt the alkali metal chloride and at least partially dissolve the oxides of lanthanum, barium, strontium, and copper and form said superconductor composition; maintaining said temperature until the oxides are substantially consumed by formation of the superconductive composition; cooling the molten solvent material to a solid; separating and recovering the superconductive composition in powder form, from the alkali metal chloride by dissolving the chloride in water. 
     
     
       3. A process for making a superconductive composition in polycrystalline powder form having the formula La 2-x  A x  CuO 4-y , wherein A is selected from the group consisting of strontium or barium, x is from about 0.1 to 0.2 and y is from 0 to about 0.2, which comprises forming an admixture comprising an alkali metal chloride selected from the group consisting of sodium chloride and potassium chloride, lanthanum oxide, a copper oxide, and at least one member of the member of the group consisting of barium oxide and strontium oxide, in amounts sufficient to produce the superconductive composition by reaction; heating the admixture to a temperature sufficient to melt the alkali metal chloride and dissolve the oxides of lanthanum, barium, strontium, and copper and form said superconductor composition; maintaining said temperature until the oxides are substantially consumed by formation of the superconductive composition; cooling the molten solvent material to a solid; separating the superconductive powder from the alkali metal chloride solvent material by dissolving the chloride solvent material in water. 
     
     
       4. The process according to claim 3 in which the admixture is heated to a temperature between about 800° C. and 1000° C. 
     
     
       5. The process according to claim 3 wherein the alkali metal chloride is an equi-molar mixture of sodium chloride and potassium chloride and the admixture is heated to a temperature between about 800° C. and 1000° C. 
     
     
       6. The process according to claim 3 wherein said alkaline earth oxide is barium oxide and barium carbonate is used as a precursor. 
     
     
       7. The process according to claim 3 wherein said alkaline earth oxide is strontium oxide and strontium carbonate is used as a precursor. 
     
     
       8. The process according to claim 3 wherein said oxide or precursor therefor ranges in particulate size up to about 100 microns. 
     
     
       9. The process according to claim 3 wherein in said formula x ranges from about 0.15 to about 0.2 and y ranges from about 0.1 to about 0.2. 
     
     
       10. The process according to claim 3 wherein said copper oxide is substantially cupric oxide.